function Person(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
}

const member = new Person("Lydia", "Hallie");
Person.getFullName = function () {
    return `${this.firstName} ${this.lastName}`;
};
//? member上肯定没有这个方法了 得把方法挂到原型上
console.log(member.getFullName());
